Heat forward LeBron James wipes his face with his jersey during a frustrating moment of Game 5 of the NBA Finals on Sunday. / Brendan Maloney, USA TODAY Sports

by Jeff Zillgitt, USA TODAY Sports

by Jeff Zillgitt, USA TODAY Sports

SAN ANTONIO - In a lighter moment earlier in the NBA Finals, Shane Battier contemplated a question and answered the way only he can.

Why can't the Miami Heat carry any edge, any momentum gained from a victory in one game into the following game?

"That is a question to ask Sigmund Freud," the Heat forward said.

It's not quite time to bring in the psychoanalysis. But it's close. The Heat have alternated wins and losses in 12 consecutive games, and the latest - a 114-104 loss to the San Antonio Spurs in Game 5 of the Finals on Sunday - puts them in a dire situation.

In a series of must-wins, the Heat face the ultimate must-win down 3-2 headed into Game 6 on Tuesday (9 p.m. ET, ABC). Either the Heat's streak ends, or the Spurs win the championship.

Since the advent of the 2-3-2 Finals format in 1985, only three teams have won the final two games at home - the 1988 Los Angeles Lakers against the Detroit Pistons, the 1994 Houston Rockets against the New York Knicks and the 2010 Lakers against the Boston Celtics.

Despite winning a franchise-record 27 consecutive games during the regular season, Miami has not won consecutive games since the end of the Eastern Conference semifinals and start of the conference finals.

"If I knew the answer, we would have won two games in (a) row," Heat forward LeBron James said.

In two of the three games in San Antonio, the Heat's defense failed. Sunday, Miami shot 43.0% from the field but 47.8% on three-pointers and scored 104 points. It wasn't a great offensive night, but it wasn't the offense as much as it was the defense that abandoned the Heat.

The Heat allowed the Spurs to shoot 60% from the field and 40.9% on three-pointers. All five Spurs starters scored in double figures, led by guard Tony Parker's 26 points and 24 points each from guards Manu Ginobili and Danny Green.

During the regular season, Miami only allowed more than 110 points a game three times in non-overtime games. It didn't happen once from Feb. 26 until the start of the Finals, and the Spurs have dropped 113 and 114 on the Heat in two of the past three games.

"It's pretty obvious that we didn't give that same defensive effort that we had in Game 4, and they picked us apart," Heat forward Chris Bosh said. "We didn't have the same effort from the get-go, and we waited until we were down double-digits to respond, and on the road you can't do that. From here on out, we can't continue to shoot ourselves in the foot like that."

Parker, Ginobili and Green were a combined 60.5% from the field, and Green - who has been on fire from deep - made 6-for-10 beyond the arc.

"Come on, they just absolutely outplayed us," Heat coach Erik Spoelstra said. "At times, they were just picking one guy out at a time and going mano y mano. That will change."

"Basically everybody on their team was taking turns off the dribble, getting by us and breaking down our defense," Spoelstra said.

In Game 3, the Spurs crushed the Heat late. In Game 5, they did it early and late. San Antonio used a 22-7 run late in the first quarter and early in the second quarter to build a 39-24 lead.

The Heat managed to come back and were within a basket multiple times throughout the third quarter, trailing 61-60 and 75-74.

But from 2:54 of the third to 9:13 of the fourth quarter, the Spurs outscored Miami 21-2 and were 8-for-12 from the field. San Antonio often out-hustled Miami and created outstanding scoring opportunities.

"This is the kind of team that I feel capitalizes on any mistakes you make," Heat guard Dwyane Wade said. "So if you're a half-second late, they capitalize it."

Now, it's Game 6 and back to Miami for at least one game.The Heat faced a similar situation in the 2011 Finals, when the Heat trailed the Dallas Mavericks 3-2. Dallas won Game 6.

"We're going to see if we're a better team than we were our first year together," Miami forward LeBron James said.

James expressed his frustration Saturday about Miami's inability to win consecutive games the past two series.

"We're well overdue when it's time for us to win consecutive games," he said. "We're at 11 or 12 straight consecutive win-loss, win-loss, win-loss. I think it's time. Enough is enough for our team."

It didn't happen in Game 5, and if the Heat are going to win a second consecutive NBA championship, they need to two consecutive games. Miami hasn't loss two consecutive games since early January. A Game 7 looks like strong possibility. But it starts with Game 6, and just like James put the pressure on himself in Game 4, he is doing it again with Miami's season on the line.

"I have to come up big, for sure in Game 6," James said. "But I believe we all have to play at a high level in order to keep the series going. So me being one of the leaders of this team, I do put a lot of pressure on myself to force a Game 7, and I look forward to the challenge."

Spoelstra spent the two off days on Friday and Saturday prepping his team to play one of its best games of the season. That didn't happen. "We were a far cry from it," Spoelstra said.

There's not much time - just Monday and a portion of Tuesday - to put his team in a better position.

"We've got an opportunity to do something special," James said. "And we look forward to it."